Severe α1‐antitrypsin (AAT) deficiency is an autosomal recessive genetic condition associated with an increased but variable risk for chronic obstructive pulmonary disease (COPD). A study was undertaken to assess the impact of chronic bronchitis, pneumonia, asthma and sex on the development of COPD in individuals with severe AAT deficiency.
The AAT Genetic Modifier Study is a multicentre family‐based cohort study designed to study the genetic and epidemiological determinants of COPD in AAT deficiency. 378 individuals (age range 33–80 years), confirmed to be homozygous for the SERPINA1 Z mutation, were included in the analyses. The primary outcomes of interest were a quantitative outcome, forced expiratory volume in 1 s (FEV1) percentage predicted, and a qualitative outcome, severe airflow obstruction (FEV1 <50% predicted).
In multivariate analysis of the overall cohort, cigarette smoking, sex, asthma, chronic bronchitis and pneumonia were risk factors for reduced FEV1 percentage predicted and severe airflow obstruction (p<0.01). Index cases had lower FEV1 values, higher smoking histories and more reports of adult asthma, pneumonia and asthma before age 16 than non‐index cases (p<0.01). Men had lower pre‐ and post‐bronchodilator FEV1 percentage predicted than women (p<0.0001); the lowest FEV1 values were observed in men reporting a history of childhood asthma (26.9%). This trend for more severe obstruction in men remained when index and non‐index groups were examined separately, with men representing the majority of non‐index individuals with airflow obstruction (71%). Chronic bronchitis (OR 3.8, CI 1.8 to 12.0) and a physician's report of asthma (OR 4.2, CI 1.4 to 13.1) were predictors of severe airflow obstruction in multivariate analysis of non‐index men but not women.
In individuals with severe AAT deficiency, sex, asthma, chronic bronchitis and pneumonia are risk factors for severe COPD, in addition to cigarette smoking. These results suggest that, in subjects severely deficient in AAT, men, individuals with symptoms of chronic bronchitis and/or a past diagnosis of asthma or pneumonia may benefit from closer monitoring and potentially earlier treatment.
Several genome-wide association studies identified the chr15q25.1 region, which includes three nicotinic cholinergic receptor genes (CHRNA5-B4) and the cell proliferation gene (PSMA4), for its association with lung cancer risk in Caucasians. A haplotype and its tagging single nucleotide polymorphisms (SNPs) encompassing six genes from IREB2 to CHRNB4 were most strongly associated with lung cancer risk (OR = 1.3; P < 10−20). In order to narrow the region of association and identify potential causal variations, we performed a fine-mapping study using 77 SNPs in a 194 kb segment of the 15q25.1 region in a sample of 448 African-American lung cancer cases and 611 controls. Four regions, two SNPs and two distinct haplotypes from sliding window analyses, were associated with lung cancer. CHRNA5 rs17486278 G had OR = 1.28, 95% CI 1.07–1.54 and P = 0.008, whereas CHRNB4 rs7178270 G had OR = 0.78, 95% CI 0.66–0.94 and P = 0.008 for lung cancer risk. Lung cancer associations remained significant after pack-year adjustment. Rs7178270 decreased lung cancer risk in women but not in men; gender interaction P = 0.009. For two SNPs (rs7168796 A/G and rs7164594 A/G) upstream of PSMA4, lung cancer risks for people with haplotypes GG and AA were reduced compared with those with AG (OR = 0.56, 95% CI 0.38–0.82; P = 0.003 and OR = 0.73, 95% CI 0.59–0.90, P = 0.004, respectively). A four-SNP haplotype spanning CHRNA5 (rs11637635 C, rs17408276 T, rs16969968 G) and CHRNA3 (rs578776 G) was associated with increased lung cancer risk (P = 0.002). The identified regions contain SNPs predicted to affect gene regulation. There are multiple lung cancer risk loci in the 15q25.1 region in African-Americans.
We examined the association between single-nucleotide polymorphisms (SNPs) previously associated with chronic obstructive pulmonary disease (COPD) and/or lung function with COPD and COPD-related phenotypes in a novel cohort of patients with severe to very severe COPD. We examined 315 cases of COPD and 330 Caucasian control smokers from Poland. We included three SNPs previously associated with COPD: rs7671167 (FAM13A), rs13180 (IREB2), and rs8034191 (CHRNA 3/5), and four SNPs associated with lung function in a genome-wide association study of general population samples: rs2070600 (AGER), rs11134242 (ADCY2), rs4316710 (THSD4), and rs17096090 (INTS12). We tested for associations with severe COPD and COPD-related phenotypes, including lung function, smoking behavior, and body mass index. Subjects with COPD were older (average age 62 versus 58 years, P < 0.01), with more pack-years of smoking (45 versus 33 pack-years, P < 0.01). CHRNA3/5 (odds ratio [OR], 1.89; 95% confidence interval [CI], 1.5–2.4; P = 7.4 × 10−7), IREB2 (OR, 0.69; 95% CI, 0.5–0.9; P = 3.4 × 10−3), and ADCY2 (OR, 1.35; 95% CI, 1.1–1.7; P = 0.01) demonstrated significant associations with COPD. FAM13A (OR, 0.8; 95% CI, 0.7–1.0; P = 0.11) approached statistical significance. FAM13A and ADCY2 also demonstrated a significant association with lung function. Thus, in severe to very severe COPD, we demonstrate a replication of association between two SNPs previously associated with COPD (CHRNA3/5 and IREB2), as well as an association with COPD of one locus initially associated with lung function (ADCY2).
chronic obstructive pulmonary disease; genetic association analysis; lung function; smoking; nicotine addiction
Genome-wide association studies of white persons with lung cancer have identified a region of extensive linkage disequilibrium on chromosome 15q25.1 that appears to be associated with both risk for lung cancer and smoking dependence. Because studying African American persons, who exhibit lower levels of linkage disequilibrium in this region, may identify additional loci that are associated with lung cancer, we genotyped 34 single-nucleotide polymorphisms (SNPs) in this region (including LOC123688, PSMA4, CHRNA5, CHRNA3, and CHRNB4 genes) in 467 African American patients with lung cancer and 388 frequency-matched African American control subjects. Associations of SNPs in LOC123688 (rs10519203; odds ratio [OR] = 1.60, 95% confidence interval [CI] = 1.25 to 2.05, P = .00016), CHRNA5 (rs2036527; OR = 1.67, 95% CI = 1.26 to 2.21, P = .00031), and CHRNA3 (rs1051730; OR = 1.81, 95% CI = 1.26 to 2.59, P = .00137) genes with lung cancer risk reached Bonferroni-corrected levels of statistical significance (all statistical tests were two-sided). Joint logistic regression analysis showed that rs684513 (OR = 0.47, 95% CI = 0.31 to 0.71, P = .0003) in CHRNA5 and rs8034191 (OR = 1.76, 95% CI = 1.23 to 2.52, P = .002) in LOC123688 were also associated with risk. The functional A variant of rs1696698 in CHRNA5 had the strongest association with lung cancer (OR = 1.98, 95% CI = 1.25 to 3.11, P = .003). These SNPs were primarily associated with increased risk for lung adenocarcinoma histology and were only weakly associated with smoking phenotypes. Thus, among African American persons, multiple loci in the region of chromosome 15q25.1 appear to be strongly associated with lung cancer risk.
Severe alpha1-antitrypsin (AAT) deficiency associated with low AAT blood concentrations is an established genetic COPD risk factor. Less is known about the respiratory health impact of variation in AAT serum concentrations in the general population. We cross-sectionally investigated correlates of circulating AAT concentrations and its association with FEV1.
In 5187 adults (2669 females) with high-sensitive c-reactive protein (CRP) levels ≤ 10 mg/l from the population-based Swiss SAPALDIA cohort, blood was collected at the time of follow-up examination for measuring serum AAT and CRP.
Female gender, hormone intake, systolic blood pressure, age in men and in postmenopausal women, as well as active and passive smoking were positively, whereas alcohol intake and BMI inversely correlated with serum AAT levels, independent of CRP adjustment. We observed an inverse association of AAT with FEV1 in the total study population (p < 0.001), that disappeared after adjustment for CRP (p = 0.28). In addition, the AAT and FEV1 association was modified by gender, menopausal status in women, and smoking.
The results of this population-based study reflect a complex interrelationship between tobacco exposure, gender related factors, circulating AAT, systemic inflammatory status and lung function.
The marked variability in individual susceptibility to the detrimental effects of smoking on lung function and findings suggest a significant genetic contribution to COPD, which has been demonstrated in several studies. The only known genetic risk factor for COPD, severe alpha 1 antitrypsin (AAT) deficiency, explains only 1–2% of cases of this disease. Screening for severe AAT should be conducted in all cases of COPD. Intravenous augmentation therapy should be combined with currently recommended treatment modalities for COPD when treating patients with COPD due to severe AAT deficiency. There is considerable interest in identifying susceptibility genes for COPD unrelated to severe AAT deficiency, as this could greatly enhance current efforts to prevent, diagnose and treat this disease by yielding novel insights into its pathogenesis. Genome-wide association studies (GWAS) of COPD and its intermediate phenotypes (e.g., lung function measures) have identified novel susceptibility loci for COPD. Some of these susceptibility loci may also influence lung function in the general population (e.g., HHIP and FAM13A), while others may affect not only COPD but other diseases related to smoking behavior (e.g., CHRNA3/CHRNA5). Although much work remains to be done, recent advances and the implementation of novel approaches to study COPD genetics (e.g., sequencing) and epigenetics are promising, and could have a profound impact on COPD management.
COPD; genetics; alpha 1 antitrypsin deficiency
The genetic risk factors for chronic obstructive pulmonary disease (COPD) are still largely unknown. To date, genome-wide association studies (GWASs) of limited size have identified several novel risk loci for COPD at CHRNA3/CHRNA5/IREB2, HHIP and FAM13A; additional loci may be identified through larger studies. We performed a GWAS using a total of 3499 cases and 1922 control subjects from four cohorts: the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); the Normative Aging Study (NAS) and National Emphysema Treatment Trial (NETT); Bergen, Norway (GenKOLS); and the COPDGene study. Genotyping was performed on Illumina platforms with additional markers imputed using 1000 Genomes data; results were summarized using fixed-effect meta-analysis. We identified a new genome-wide significant locus on chromosome 19q13 (rs7937, OR = 0.74, P = 2.9 × 10−9). Genotyping this single nucleotide polymorphism (SNP) and another nearby SNP in linkage disequilibrium (rs2604894) in 2859 subjects from the family-based International COPD Genetics Network study (ICGN) demonstrated supportive evidence for association for COPD (P = 0.28 and 0.11 for rs7937 and rs2604894), pre-bronchodilator FEV1 (P = 0.08 and 0.04) and severe (GOLD 3&4) COPD (P = 0.09 and 0.017). This region includes RAB4B, EGLN2, MIA and CYP2A6, and has previously been identified in association with cigarette smoking behavior.
Severe α1-antitrypsin (AAT) deficiency is a proven genetic risk factor for chronic obstructive pulmonary disease (COPD), especially in individuals who smoke. There is marked variability in the development of lung disease in individuals homozygous (PI ZZ) for this autosomal recessive condition, suggesting that modifier genes could be important. We hypothesized that genetic determinants of obstructive lung disease may be modifiers of airflow obstruction in individuals with severe AAT deficiency. To identify modifier genes, we performed family-based association analyses for 10 genes previously associated with asthma and/or COPD, including IL10, TNF, GSTP1, NOS1, NOS3, SERPINA3, SERPINE2, SFTPB, TGFB1, and EPHX1. All analyses were performed in a cohort of 378 PI ZZ individuals from 167 families. Quantitative spirometric phenotypes included forced expiratory volume in one second (FEV1) and the ratio of FEV1/forced vital capacity (FVC). A qualitative phenotype of moderate-to-severe COPD was defined for individuals with FEV1 ⩽ 50 percent predicted. Six of 11 single-nucleotide polymorphisms (SNPs) in IL10 (P = 0.0005–0.05) and 3 of 5 SNPs in TNF (P = 0.01–0.05) were associated with FEV1 and/or FEV1/FVC. IL10 SNPs also demonstrated association with the qualitative COPD phenotype. When phenotypes of individuals with a physician's diagnosis of asthma were excluded, IL10 SNPs remained significantly associated, suggesting that the association with airflow obstruction was independent of an association with asthma. Haplotype analysis of IL10 SNPs suggested the strongest association with IL10 promoter SNPs. IL10 is likely an important modifier gene for the development of COPD in individuals with severe AAT deficiency.
chronic obstructive pulmonary disease; genetic modifiers; interleukin 10; family-based association analysis
Chronic obstructive pulmonary disease (COPD) is characterized by incompletely reversible airflow obstruction associated with inflammation in which monocytes/macrophages are the predominant inflammatory cells. The only known genetic factor related to COPD is inherited PiZZ deficiency of α1-antitrypsin (AAT), an inhibitor of serine proteases.
We investigated the basal and LPS-stimulated release of pro-inflammatory molecules from blood monocytes isolated from age and gender matched healthy (n = 30) and COPD (n = 20) individuals with and without AAT deficiency.
After 18 h of cell culture the basal release of MMP-9 was 2.5-fold, p < 0.02 greater, whereas IL-8 was 1.8-fold (p < 0.01) lower from COPD patient monocytes than from controls. LPS-stimulated release of IL-6 and MCP-1 was greater from COPD patient's monocytes relative to controls, while activation of control cells resulted in enhanced secretion of ICAM-1 and MMP-9 compared to COPD patients. Independent of disease status, monocytes from PiZZ AAT carriers released less TNFα (by 2.3-fold, p < 0.03).
The basal and LPS-stimulated secretion of specific pro-inflammatory molecules from circulating monocytes differs between healthy and COPD subjects. These findings may be valuable for further studies on the mechanisms involved in recruitment and activation of inflammatory cells in COPD.
Three recent genome-wide association studies identified associations between markers in the chromosomal region 15q24-25.1 and the risk of lung cancer. We conducted a genome-wide association analysis to investigate associations between single-nucleotide polymorphisms (SNPs) and the risk of lung cancer, in which we used blood DNA from 194 case patients with familial lung cancer and 219 cancer-free control subjects. We identified associations between common sequence variants at 15q24-25.1 (that spanned LOC123688 [a hypothetical gene], PSMA4, CHRNA3, CHRNA5, and CHRNB4) and lung cancer. The risk of lung cancer was more than fivefold higher among those subjects who had both a family history of lung cancer and two copies of high-risk alleles rs8034191 (odds ratio [OR] = 7.20, 95% confidence interval [CI] = 2.21 to 23.37) or rs1051730 (OR = 5.67, CI = 2.21 to 14.60, both of which were located in the 15q24-25.1 locus, than among control subjects. Thus, further research to elucidate causal variants in the 15q24-25.1 locus that are associated with lung cancer is warranted.
BACKGROUND: Severe alpha 1-antitrypsin (AAT) deficiency (PiZZ) is associated with an increased risk of lung emphysema, especially in smokers. The aim of this study was to identify risk factors other than smoking for declining lung function. METHODS: Lung function was studied in 225 self-reported never-smoking PiZZ individuals included in the Swedish AAT deficiency register. RESULTS: Lung function was poorer in men than in women (mean (SD) forced expiratory volume in one second (FEV1) 80 (30) versus 88 (17)% predicted) despite the fact that the men were younger (mean (SD) age 45 (18) versus 51 (17) years), and poorer in those aged 50 or older than in those aged under 50 (mean (SD) FEV1 70 (30) versus 98 (16)% predicted). Self-reported occupational exposure to gas, fumes, or dust occurred more frequently in men than in women. In those aged 50 or older lung function was lower in individuals exposed to airway irritants than those who were not exposed (mean (SD) FEV1 63 (29) versus 76 (31)% predicted). Male sex, increasing age, and previous symptoms of wheezing were independent risk factors for lung function impairment, and male sex, wheeziness, and occupational exposure to airway irritants were independent risk factors in the subjects aged 50 years or more. CONCLUSIONS: In non-smoking PiZZ individuals lung function declines with increasing age, especially after 50. Men are at greater risk of lung function deterioration than women. Asthmatic symptoms and occupational exposure to airway irritants appear to constitute additional risk factors.
Recently, genetic association findings for nicotine dependence, smoking behavior, and smoking-related diseases converged to implicate the chromosome 15q25.1 region, which includes the CHRNA5-CHRNA3-CHRNB4 cholinergic nicotinic receptor subunit genes. In particular, association with the nonsynonymous CHRNA5 SNP rs16969968 and correlates has been replicated in several independent studies. Extensive genotyping of this region has suggested additional statistically distinct signals for nicotine dependence, tagged by rs578776 and rs588765. One goal of the Consortium for the Genetic Analysis of Smoking Phenotypes (CGASP) is to elucidate the associations among these markers and dichotomous smoking quantity (heavy versus light smoking), lung cancer, and chronic obstructive pulmonary disease (COPD). We performed a meta-analysis across 34 datasets of European-ancestry subjects, including 38,617 smokers who were assessed for cigarettes-per-day, 7,700 lung cancer cases and 5,914 lung-cancer-free controls (all smokers), and 2,614 COPD cases and 3,568 COPD-free controls (all smokers). We demonstrate statistically independent associations of rs16969968 and rs588765 with smoking (mutually adjusted p-values<10−35 and <10−8 respectively). Because the risk alleles at these loci are negatively correlated, their association with smoking is stronger in the joint model than when each SNP is analyzed alone. Rs578776 also demonstrates association with smoking after adjustment for rs16969968 (p<10−6). In models adjusting for cigarettes-per-day, we confirm the association between rs16969968 and lung cancer (p<10−20) and observe a nominally significant association with COPD (p = 0.01); the other loci are not significantly associated with either lung cancer or COPD after adjusting for rs16969968. This study provides strong evidence that multiple statistically distinct loci in this region affect smoking behavior. This study is also the first report of association between rs588765 (and correlates) and smoking that achieves genome-wide significance; these SNPs have previously been associated with mRNA levels of CHRNA5 in brain and lung tissue.
Nicotine binds to cholinergic nicotinic receptors, which are composed of a variety of subunits. Genetic studies for smoking behavior and smoking-related diseases have implicated a genomic region that encodes the alpha5, alpha3, and beta4 subunits. We examined genetic data across this region for over 38,000 smokers, a subset of which had been assessed for lung cancer or chronic obstructive pulmonary disease. We demonstrate strong evidence that there are at least two statistically independent loci in this region that affect risk for heavy smoking. One of these loci represents a change in the protein structure of the alpha5 subunit. This work is also the first to report strong evidence of association between smoking and a group of genetic variants that are of biological interest because of their links to expression of the alpha5 cholinergic nicotinic receptor subunit gene. These advances in understanding the genetic influences on smoking behavior are important because of the profound public health burdens caused by smoking and nicotine addiction.
α-1 antitrypsin (AAT) deficiency results from mutations of the protease inhibitor (PI). The AAT gene is mapped on chromosome 14 and has been associated with chronic liver disease and chronic obstructive pulmonary disease (COPD).
To determine the frequency of AAT mutations on S and Z carrier alleles in healthy Saudi individuals from Qassim Province in Saudi Arabia.
Patients and Methods:
A total of 158 healthy, unrelated participants from Qassim Province were recruited. They were genotyped for the two AAT-deficiency alleles, PI*S and PI*Z, using polymerase chain reaction, with primers designed throughout to mediate site-directed mutagenesis.
Of the 158 subjects, 11.39% were carriers for the S mutation (i.e., had the MS genotype), whereas 2.53% were carriers for the Z mutation (i.e., had the MZ genotype). The SZ genotype was present in 3.8% of subjects, while the homozygous genotype SS was present in 1.9% of subjects. No subjects showed the ZZ mutant genotype. Accordingly, frequency of the mutant S and Z alleles of AAT gene was 9.49% and 3.19%, respectively.
The results obtained showed a high prevalence of the AAT deficiency allele in the Saudi population. This probably warrants adoption of a screening program for at-risk individuals, so that they might initiate adequate prophylactic measures.
α-1 antitrypsin; Saudi Arabia; S allele; Z allele
Genetic factors are known to contribute to COPD susceptibility and these factors are not fully understood. Conflicting results have been reported for many genetic studies of candidate genes based on their role in the disease. Genome-wide association studies in combination with expression profiling have identified a number of new candidates including IREB2. A meta-analysis has implicated transforming growth factor beta-1 (TGFbeta1) as a contributor to disease susceptibility.
We have examined previously reported associations in both genes in a collection of 1017 white COPD patients and 912 non-diseased smoking controls. Genotype information was obtained for seven SNPs in the IREB2 gene, and for four SNPs in the TGFbeta1 gene. Allele and genotype frequencies were compared between COPD cases and controls, and odds ratios were calculated. The analysis was adjusted for age, sex, smoking and centre, including interactions of age, sex and smoking with centre.
Our data replicate the association of IREB2 SNPs in association with COPD for SNP rs2568494, rs2656069 and rs12593229 with respective adjusted p-values of 0.0018, 0.0039 and 0.0053. No significant associations were identified for TGFbeta1.
These studies have therefore confirmed that the IREB2 locus is a contributor to COPD susceptibility and suggests a new pathway in COPD pathogenesis invoking iron homeostasis.
Alpha-1 antitrypsin deficiency (AATD) is a rare genetic disease that results from mutations in the alpha-1 antitrypsin (AAT) gene. The mutant AAT protein aggregates and accumulates in the liver leading to AATD liver disease, which is only treatable by liver transplant. The PiZ transgenic mouse strain expresses a human AAT (hAAT) transgene that contains the AATD-associated Glu342Lys mutation. PiZ mice exhibit many AATD symptoms, including AAT protein aggregates, increased hepatocyte death, and liver fibrosis. In the present study, we systemically treated PiZ mice with an antisense oligonucleotide targeted against hAAT (AAT-ASO) and found reductions in circulating levels of AAT and both soluble and aggregated AAT protein in the liver. Furthermore, AAT-ASO administration in these animals stopped liver disease progression after short-term treatment, reversed liver disease after long-term treatment, and prevented liver disease in young animals. Additionally, antisense oligonucleotide treatment markedly decreased liver fibrosis in this mouse model. Administration of AAT-ASO in nonhuman primates led to an approximately 80% reduction in levels of circulating normal AAT, demonstrating potential for this approach in higher species. Antisense oligonucleotides thus represent a promising therapy for AATD liver disease.
Panniculitis is a recognized but unusual complication of a severe deficiency of α1-antitrypsin (AAT), with fewer than 100 cases described to date. Like the pathogenesis of emphysema in severe PiZZ deficiency of AAT, panniculitis has been hypothesized to be an inflammatory process, possibly related to Z AAT polymer formation and to an unopposed anti-inflammatory screen in the context of deficient serum levels of AAT. The current report presents a 31-year-old woman with PiZZ AAT deficiency-associated panniculitis. Our case extends current knowledge of AAT-associated panniculitis in 2 ways: (1) we demonstrate Z-type AAT polymers in the skin, which supports the inflammatory pathogenesis of panniculitis and the potential pro-inflammatory role of polymers; (2) we show that a high dose and long-term use of intravenous augmentation therapy (90 mg/kg body weight once weekly during 3 years) can ameliorate the frequency and severity of panniculitis associated with AAT deficiency.
α1-Antitrypsin; Polymers; Panniculitis; Inflammation; Augmentation therapy
Several infrequent genetic polymorphisms in the SERPINA1 gene are known to substantially reduce concentration of alpha1-antitrypsin (AAT) in the blood. Since low AAT serum levels fail to protect pulmonary tissue from enzymatic degradation, these polymorphisms also increase the risk for early onset chronic obstructive pulmonary disease (COPD). The role of more common SERPINA1 single nucleotide polymorphisms (SNPs) in respiratory health remains poorly understood.
We present here an agnostic investigation of genetic determinants of circulating AAT levels in a general population sample by performing a genome-wide association study (GWAS) in 1392 individuals of the SAPALDIA cohort.
Five common SNPs, defined by showing minor allele frequencies (MAFs) >5%, reached genome-wide significance, all located in the SERPINA gene cluster at 14q32.13. The top-ranking genotyped SNP rs4905179 was associated with an estimated effect of β = −0.068 g/L per minor allele (P = 1.20*10−12). But denser SERPINA1 locus genotyping in 5569 participants with subsequent stepwise conditional analysis, as well as exon-sequencing in a subsample (N = 410), suggested that AAT serum level is causally determined at this locus by rare (MAF<1%) and low-frequent (MAF 1–5%) variants only, in particular by the well-documented protein inhibitor S and Z (PI S, PI Z) variants. Replication of the association of rs4905179 with AAT serum levels in the Copenhagen City Heart Study (N = 8273) was successful (P<0.0001), as was the replication of its synthetic nature (the effect disappeared after adjusting for PI S and Z, P = 0.57). Extending the analysis to lung function revealed a more complex situation. Only in individuals with severely compromised pulmonary health (N = 397), associations of common SNPs at this locus with lung function were driven by rarer PI S or Z variants. Overall, our meta-analysis of lung function in ever-smokers does not support a functional role of common SNPs in the SERPINA gene cluster in the general population.
Low levels of alpha1-antitrypsin (AAT) in the blood are a well-established risk factor for accelerated loss in lung function and chronic obstructive pulmonary disease. While a few infrequent genetic polymorphisms are known to influence the serum levels of this enzyme, the role of common genetic variants has not been examined so far. The present genome-wide scan for associated variants in approximately 1400 Swiss inhabitants revealed a chromosomal locus containing the functionally established variants of AAT deficiency and variants previously associated with lung function and emphysema. We used dense genotyping of this genetic region in more than 5500 individuals and subsequent conditional analyses to unravel which of these associated variants contribute independently to the phenotype's variability. All associations of common variants could be attributed to the rarer functionally established variants, a result which was then replicated in an independent population-based Danish cohort. Hence, this locus represents a textbook example of how a large part of a trait's heritability can be hidden in infrequent genetic polymorphisms. The attempt to transfer these results to lung function furthermore suggests that effects of common variants in this genetic region in ever-smokers may also be explained by rarer variants, but only in individuals with hampered pulmonary health.
Alpha-1 antitrypsin (AAT) deficiency is an inherited genetic disorder currently diagnosed in approximately 5,000 people in the United States. Although some individuals with AAT deficiency are asymptomatic, the condition often leads to deterioration of lung function in adults and is associated with emphysema, asthma, chronic obstructive pulmonary disease, and other respiratory diseases. In children, AAT deficiency can result in severe liver disease, including fatal cirrhosis in newborn infants. Although much is known about the clinical pathology of AAT deficiency, researchers are just beginning to characterize environmental, occupational, and genetic modifiers affecting the onset and progression of diseases related to AAT deficiency. On 19 August 2002, a group of basic scientists, clinicians, environmental health researchers, and public interest groups gathered at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina, to discuss ongoing research on these topics. The goals of this workshop were to a) assess the present state of knowledge regarding environmental and occupational risk factors contributing to AAT deficiency morbidity and mortality, b) define future research needs in this area, and c) explore collaborative opportunities to advance understanding of risk factors affecting the progression of AAT deficiency-related disease. Participants agreed that new research initiatives in these areas represent an opportunity to benefit both basic science, through enhanced understanding of gene-environment interaction, and the AAT deficiency patient community, through innovative new approaches to disease management and treatment.
Recombinant adeno-associated virus (rAAV) vectors offer promise for the gene therapy of α1-antitrypsin (AAT) deficiency. In our prior trial, an rAAV vector expressing human AAT (rAAV1-CB-hAAT) provided sustained, vector-derived AAT expression for >1 year. In the current phase 2 clinical trial, this same vector, produced by a herpes simplex virus complementation method, was administered to nine AAT-deficient individuals by intramuscular injection at doses of 6.0×1011, 1.9×1012, and 6.0×1012 vector genomes/kg (n=3 subjects/dose). Vector-derived expression of normal (M-type) AAT in serum was dose dependent, peaked on day 30, and persisted for at least 90 days. Vector administration was well tolerated, with only mild injection site reactions and no serious adverse events. Serum creatine kinase was transiently elevated on day 30 in five of six subjects in the two higher dose groups and normalized by day 45. As expected, all subjects developed anti-AAV antibodies and interferon-γ enzyme-linked immunospot responses to AAV peptides, and no subjects developed antibodies to AAT. One subject in the mid-dose group developed T cell responses to a single AAT peptide unassociated with any clinical effects. Muscle biopsies obtained on day 90 showed strong immunostaining for AAT and moderate to marked inflammatory cell infiltrates composed primarily of CD3-reactive T lymphocytes that were primarily of the CD8+ subtype. These results support the feasibility and safety of AAV gene therapy for AAT deficiency, and indicate that serum levels of vector-derived normal human AAT >20 μg/ml can be achieved. However, further improvements in the design or delivery of rAAV-AAT vectors will be required to achieve therapeutic target serum AAT concentrations.
Flotte and colleagues report on a phase 2 trial in which the same α1-antitrypsin (AAT) AAV vector as in phase 1 is administered intramuscularly to nine AAT-deficient individuals at one of three doses. Vector-derived expression of normal (M-type) AAT in serum is shown to be dose dependent, peaks on day 30, and persists for at least 90 days, although AAT levels were sub-therapeutic.
Individuals with severe Z α1-antitrypsin (AAT) deficiency have a considerably increased risk of developing chronic obstructive lung disease (COPD). It has been hypothesized that compensatory increases in levels of other protease inhibitors mitigate the effects of this AAT deficiency. We analysed plasma levels of AAT, α1-antichymotrypsin (ACT) and secretory leukocyte protease inhibitor (SLPI) in healthy (asymptomatic) and COPD subjects with and without AAT deficiency.
Studied groups included: 71 asymptomatic AAT-deficient subjects (ZZ, n = 48 and SZ, n = 23, age 31 ± 0.5) identified during Swedish neonatal screening for AAT deficiency between 1972 and 1974; age-matched controls (MM, n = 57, age 30.7 ± 0.6); older asymptomatic ZZ (n = 10); healthy MM (n = 20, age 53 ± 9.6); and COPD patients (ZZ, n = 10, age 47.4 ± 11 and MM, n = 10, age 59.4 ± 6.7). Plasma levels of SLPI, AAT and ACT were analysed using ELISA and immunoelectrophoresis.
No significant difference was found in plasma ACT and SLPI levels between the healthy MM and the ZZ or SZ subjects in the studied groups. Independent of the genetic variant, subjects with COPD (n = 19) had elevated plasma levels of SLPI and ACT relative to controls (n = 153) (49.5 ± 7.2 vs 40.7 ± 9.1 ng/ml, p < 0.001 and 0.52 ± 0.19 vs 0.40 ± 0.1 mg/ml, p < 0.05, respectively).
Our findings show that plasma levels of ACT and SLPI are not elevated in subjects with genetic AAT deficiency compared MM controls and do not appear to compensate for the deficiency of plasma AAT.
Genetic association studies have demonstrated the importance of variants in the CHRNA5-CHRNA3-CHRNB4 cholinergic nicotinic receptor subunit gene cluster on chromosome 15q24-25.1 in risk for nicotine dependence, smoking, and lung cancer in populations of European descent. We have now carried out a detailed study of this region using dense genotyping in both European- and African-Americans.
We genotyped 75 known single-nucleotide-polymorphisms (SNPs) and one sequencing-discovered SNP in an African-American (AA) sample (N = 710) and European-American (EA) sample (N = 2062). Cases were nicotine-dependent and controls were non-dependent smokers.
The non-synonymous CHRNA5 SNP rs16969968 is the most significant SNP associated with nicotine dependence in the full sample of 2772 subjects (p = 4.49×10−8, OR 1.42 (1.25–1.61)) as well as in AAs only (p = 0.015, OR = 2.04 (1.15–3.62)) and EAs only (p = 4.14×10−7, OR = 1.40 (1.23–1.59)). Other SNPs that have been shown to affect mRNA levels of CHRNA5 in EAs are associated with nicotine dependence in AAs but not in EAs. The CHRNA3 SNP rs578776, which has low correlation with rs16969968, is associated with nicotine dependence in EAs but not in AAs. Less common SNPs (frequency ≤ 5%) also are associated with nicotine dependence.
In summary, multiple variants in this gene cluster contribute to nicotine dependence risk, and some are also associated with functional effects on CHRNA5. The non-synonymous SNP rs16969968, a known risk variant in European-descent populations, is also significantly associated with risk in African-Americans. Additional SNPs contribute in distinct ways to risk in these two populations.
genetic association; smoking; cholinergic nicotinic receptors; nicotinic acetylcholine receptors
Alpha‐1‐antitrypsin (AAT) deficiency is a relatively common genetic disorder that can lead to the development of pulmonary disorders. Diagnosis of AAT deficiency is typically performed by isoelectric focusing (IEF) protein phenotyping in concert with determination of AAT serum concentration levels. The “P” phenotypic variant is associated with several known genetic variants that are found at unknown relative frequencies.
To investigate the genetic variation of “P” alleles in patient samples.
A DNA sequencing protocol for the full AAT coding region from serum was developed. Additionally, a retrospective evaluation of AAT concentrations in serum samples containing “P” allele IEF phenotype variants was undertaken.
“P” phenotypic variants are observed in ∼1 of every 900 samples received in the reference laboratory. Heterozygous “MP” allele samples exhibited a wide range of serum protein concentrations. Genotyping revealed the presence of the deleterious Plowell variant in six heterozygous MP samples, two heterozygous PZ samples, and one homozygous PP sample. A non‐deleterious Pst albans variant was observed in a single MP sample. A novel heterozygous AAT M“P” variant, Psalt lake was identified, that did not exhibit a reduced AAT serum concentration.
Genetic heterogeneity is present in clinical “P” phenotype variants identified by IEF, and the deleterious Plowell variant appears to be relatively common. Sequencing of “P” phenotype variants can provide useful clinical information, especially when the “P” phenotype variant is paired with a deficiency phenotype allele.
alpha‐1‐antitrypsin; isoelectric focusing; P variant; full gene sequencing
Alpha-1-antitrypsin (AAT) deficiency is a genetic condition that increases the risk of developing lung and liver disease, as well as other associated conditions. Most treatment of affected individuals is not specifically directed at AAT deficiency but focuses on the resultant disease state. The only currently available specific therapeutic agent—namely, intravenous augmentation with plasma derived AAT protein—is marketed in a limited number of countries. Treatments aimed at correcting the underlying genetic abnormality, supplementing or modifying the gene product, and halting or reversing organ injury are now beginning to emerge. These innovative approaches may prove effective at modifying or eliminating diseases association with AAT deficiency.
Previous studies of the natural history of alpha-1-antitrypsin (AAT) deficiency are mostly based on highly selected patients. The aim of this study was to analyse the mortality of PiZZ individuals.
Data from 1339 adult PiZZ individuals from the Swedish National AAT Deficiency Registry, followed from 1991 to 2008, were analysed. Forty-three percent of these individuals were identified by respiratory symptoms (respiratory cases), 32% by liver diseases and other diseases (non-respiratory cases) and 25% by screening (screened cases). Smoking status was divided into two groups: smokers 737 (55%) and 602 (45%) never-smokers.
During the follow-up 315 individuals (24%) died. The standardised mortality rate (SMR) for respiratory cases was 4.70 (95% Confidence Interval (CI) 4.10-5.40), 3.0 (95%CI 2.35-3.70) for the non-respiratory cases and 2.30 (95% CI 1.46-3.46) for the screened cases. The smokers had a higher mortality risk than never-smokers, with a SMR of 4.80 (95%CI 4.20-5.50) for the smokers and 2.80(95%CI 2.30-3.40) for the never-smokers. The Rate Ratio (RR) was 1.70 (95% CI 1.35-2.20). Also among the screened cases, the mortality risk for the smokers was significantly higher than in the general Swedish population (SMR 3.40 (95% CI 1.98-5.40).
Smokers with severe AAT deficiency, irrespective of mode of identification, have a significantly higher mortality risk than the general Swedish population.
Alpha1-antitrypsin (AAT) deficiency is a hereditary disorder associated with reduced AAT plasma levels, predisposing adults to pulmonary emphysema. The most common genetic AAT variants found in patients are the mildly deficient S and the severely deficient Z alleles, but several other pathogenic rare alleles have been reported. While the plasma AAT deficiency is a common trait of the disease, only a few AAT variants, including the prototypic Z AAT and some rare variants, form cytotoxic polymers in the endoplasmic reticulum of hepatocytes and predispose to liver disease. Here we report the identification of three new rare AAT variants associated to reduced plasma levels and characterize their molecular behaviour in cellular models. The variants, called Mpisa (Lys259Ile), Etaurisano (Lys368Glu) and Yorzinuovi (Pro391His), showed reduced secretion compared to control M AAT, and accumulated to different extents in the cells as ordered polymeric structures resembling those formed by the Z variant. Structural analysis of the mutations showed that they may facilitate polymerization both by loosening ‘latch’ interactions constraining the AAT reactive loop and through effects on core packing. In conclusion, the new AAT deficiency variants, besides increasing the risk of lung disease, may predispose to liver disease, particularly if associated with the common Z variant. The new mutations cluster structurally, thus defining a region of the AAT molecule critical for regulating its conformational state.